Sulphides and disulphides have curative power. Dimethylsulphide is used for internal treatment, di-o-aminophenyldisulphide is used for intramuscular injections. Diallyl sulphide is also a medicament. Methyl selenide has some effect on the internal parts of the body(33). Hanzlik and Tarr(34) at the American University Experimental Station, showed that a number of selenium compounds act as skin irritants: e.g., dichlorodiethyl selenide, dichlorovinyl selenide, trichlorodiethyl selenide and selenium mustard oil. The first mentioned proved as potent as the sulphide, but the others fell somewhat below in their effects. Diantipyryl selenide is another therapeutical agent(35). The diselenides occupy an important place of their own. The selenophenols do not remain unchanged in the air, but are always oxidized to the diselenides, which can be again reduced to the selenophenols. So far only the diselenides of anthraquinone and their phenols are recognized remedies(36). TINCTORIAL REVIEW Many of the seleno organic compounds are colored, while the corresponding sulphur derivatives are colorless. HC-CH HC-CH || || || || HC CH HC CH \ / \ / O S Furane, colorless Thiophene, colorless liquid liquid HC--CH HC--CH || || || || HC CH HC CH \ / \ / NH Se Pyrrol, colorless liq. Selenophene, yellow liq. but turns brownish in air after repeated extraction[B] This brings selenophene more akin to pyrrole than thiophene, but the group -NH- in the molecule of pyrrole is an auxochrome. The selenium atom in a cyclic compound also acts like an auxochrome. Selenoantipyrine(37), C₆H₅ N / \ CH₃N CSe | | CH₃C===CH forms pure yellow crystals from alcohol, while the corresponding compounds of oxygen and sulphur are colorless. Similarly, the 2-methyl-4-selenoquinazolone is deep brown in color, while the thio compound, prepared by Bogert and Hand(38) is light brown or yellow and the corresponding oxygen compound is colorless or nearly so. Diethyl selenide (C₂H₅)₂Se, is a yellowish heavy oil of unpleasant odor. It combines readily with chlorine to form a chloride (C₂H₅)₂SeCl₂, and the latter is oxidized by nitric acid to form an oxide (C₂H₅)₂SeO,(39). Diethyl sulphide is a colorless syrupy liquid, as well as diethyl amine and diethyl ether. The gradation of color is quite pronounced in the case of selenonaphthene quinone(40). CO CO CO CO /\ / \ /\ / \ /\ / \ /\ / \ | | CO | | CO | | CO | | CO \/ \ / \/ \ / \/ \ / \/ \ / O S NH Se